Shrub 1-3 m, or even a small tree; lvs opposite or occasionally in whorls of 3, ovate-oblong or lance-oblong, 8-15 cm; stipules deltoid, 2-3 mm, glandular- dentate; heads 3 cm thick, on elongate peduncles terminating the stems or from the upper axils, the fls intermingled with filiform-clavate bractlets; cor white, 5-8 mm; fr obconic, angular, 5 mm; 2n=44. Swamps and streamsides; N.S., N.B. and Que. to Minn., s. to Mex. and W.I. June-Aug. Most of our plants are glabrous or inconspicuously hairy, and represent var. occidentalis. The chiefly southern var. pubescens Raf., with the twigs and lower lf-surfaces evidently soft-hairy, extends n. to Va., Ind. and Mo.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.